The bill's approval gives the IRS harsh new criminal penalties for use against those in the underground criminal economy. According to Grassley's office, the majority of the victims of sex trafficking -- those who are often smuggled in from other counties and virtually imprisoned in a house set up for prostitution -- are girls ages 13 to 17.

'A no-brainer'

"It's a no-brainer to have the IRS go after sex traffickers," Grassley said. "Prosecuting tax code violations can get these guys off the street and yank from their grasp the girls and women they exploit. This crime is right under our noses in the United States, and it's especially horrible when under-age girls are being held prisoner. The thugs who run the trafficking rings are exploiting society's poorest girls and women for personal gain."

Asked Tuesday about whether taxing sex workers would somehow lend legitimacy to them, a spokesman for Grassley said that the goal of the legislation would not be to legitimize the individuals but rather to find "yet another alternative to track the money flowing in this industry to get at potential criminals."

The bill also calls for more jail time for sex workers. According to Grassley's office, in the past, the IRS has been saddled with having to prove how much income a sexual worker earned in order to show that he or she has not been paying enough income tax. Grassley's proposal will help overcome those obstacles. For example, if a trafficker has failed to file W-2s for five women (employees), the maximum penalty would be 10 years in prison per failure to file, a total of 50 years.

Grassley used the example of gangster Al Capone, who was eventually jailed on tax evasion charges. The bill, according to a spokesman for Grassley, will use the federal tax code to shut down illegal sex workers who are hard to get by way of other federal criminal laws and are not targeted by state law enforcement.

"For the first time ever, the tax code would help put behind bars the criminals who are making money in the underground economy by selling sexual access to girls and women," the spokesman said in an e-mail statement.

Strip clubs a target?

Carol Leigh, a representative of BAYSWAN, a San Francisco Bay area sex worker advocacy network, criticized the legislation as being shortsighted.

"Forced labor, kidnapping should be targeted, but this legislation broadly targets the sex trade in general, and could target your local strip club," Leigh said. "Those of us who work in the industry understand that this does nothing to improve conditions in our industry.

"We want laws enforced against those who abuse us, against those who are violent, and enforcement of labor regulations. That is the only truly effective way to protect the welfare of the women who work in the industry."

The sex trafficking bill proposed by Grassley was part of a scheduled Senate Finance Committee good government tax bill.